1. Field of the Invention
The present invention relates to communication networks and, more particularly, to a method and apparatus for increasing the scalability of Ethernet Operation Administration and Maintenance (OAM).
2. Description of the Related Art
Data communication networks may include various routers, switches, bridges, hubs, and other network devices coupled together and configured to pass data to one another. These devices will be referred to herein as “network elements.” Data is communicated through the data communication network by passing protocol data units, such as frames, packets, cells, or segments, between the network elements by utilizing one or more communication links. A particular protocol data unit may be handled by multiple network elements and cross multiple communication links as it travels between its source and its destination over the network.
Ethernet is a well known networking protocol that has been defined by the Institute of Electrical and Electronics Engineers (IEEE) as standard 802. Ethernet was developed to be used to implement local area networks in enterprises such as businesses and campuses. Since it wasn't originally developed as a long haul transport technology, other technologies were initially used to transport data between Ethernet networks. For example, when two Ethernet networks were to be connected over a service provider's network, the Ethernet frames would be converted to protocol data units formed according to a transport protocol in use on the service provider's network, and then carried over the network. The Ethernet frames would then be recovered at the other side of the service provider's network and passed onto the second Ethernet network.
As the underlying networks have evolved and larger numbers of Ethernet networks are being connected together, it has become more desirable to use Ethernet as a transport technology on service provider networks. Additionally, as Ethernet has increased in popularity, the price for Ethernet ports has dropped, thus potentially making Ethernet a cost-effective alternative to traditional transport technologies.
A portion of an example communication network 10 is shown in FIG. 1. In the example network 10 of FIG. 1, each customer site 11 is connected to the network 10 using one or more Customer Edge (CE) network elements 12. The CE network elements 12 are connected to Provider Edge (PE) network elements 14, which in turn are connected to Provider (P) network elements 16. Network elements within the service provider's network that interface CE network elements will be referred to herein as Provider Edge (PE) network elements 14, whereas network elements within the service provider's network that only interface other service provider network elements and do not interface CE network elements will be referred to as Provider (P) network elements 16. CE-PE links 18, PE-P links 20, and P-P links 22 are formed on the network to enable data to be transported across the communication network.
When Ethernet is to be used on a service provider network, paths through the network are statically provisioned between pairs of PE network elements, and data traffic between these PE network elements will then follow the established paths through the network. As shown in FIG. 2, generally, multiple paths 30 may be statically provisioned through the network so that traffic between the PEs may traverse the network.
FIG. 3 shows an example of a path through a network such as the network of FIG. 1. As shown in FIG. 3, each network element along the path has one or more interfaces that allow it to connect to links 18, 20, 22, along the path. One type of port that may be used to interface a CE-PE links 18 on a PE network element is a User to Network Interface (UNI). For example, as shown in FIG. 3, the CE network element 12 includes an uplink interface 24 connected to link 18, and the PE network element 14 includes a UNI interface 26 connected to link 18. These interfaces enable messages to be passed between the CE and PE network elements over link 18 and otherwise allow the network elements to coordinate the exchange of data over link 18.
Within the network, links are interfaced using ports configured as Network to Network Interfaces (NNI). Thus, for example, PE network element 14 includes an NNI interface 28 configured to interface link PE-P link 20, and the P network element 16 includes several NNI interfaces configured to connect to PE-P links 20 and P-P links 22.
Data that is to be transmitted between end users will form flows of data on the network. The portion of the flow of data that extends between the UNI interfaces on the network will be referred to herein as a service instance. For example, FIG. 4 illustrates a particular flow of data 32 between a first computer 34 on a local area network 36 connected to a first CE network element (CE1), and a second computer 28 on a second local area network 40 connected to a second CE network element (CE2). The flow of data, in this example, extends between two computers which may be servers, personal computers, tablet computers, or other types of electronic devices capable of exchanging data over a network. The data flow may be associated with a virtual private network or another logical flow of data between the two devices. At the network level, the flow of data will be carried on a service instance extending between a pair of the UNIs 26 on PE network elements.
Multiple service instances may be provisioned through a particular UNI interface on a PE network element. Service instances through a common pair of UNIs on a pair of PEs on the network 10 may be logically grouped to form a service group.
If Ethernet is to be used in a service provider's network, it is necessary to implement Operation, Administration, and Maintenance (OAM) functions in Ethernet so that service providers can monitor service availability on the network. OAM functions generally include transmission of ping, trace route, and keep-alive messages, although other messages may be supported as well. Transmission of OAM messages allows the service provider to monitor configuration as well as connectivity on the network.
Conventionally, Ethernet OAM has been run at the service instance or service group level to verify connectivity. Since there may be hundreds of service groups, and each of the service groups may include hundreds or more service instances, running Ethernet OAM at the service instance or service group level may consume a considerable amount of bandwidth on the network. For example, if each service instance or service group transmits OAM messages sufficiently regularly to guarantee fault detection and restoration within 50 ms of fault occurrence, it may be necessary to allocate a significant portion of the available bandwidth to implementing OAM on the network. As the network increases in size, the number of Ethernet OAM messages that must be carried may increase to the point where scalability of the Ethernet network is impeded. Thus, it would be advantageous to provide a method and apparatus for increasing the scalability of Ethernet OAM.